GB853286A - Improvements in or relating to cold cathode switching devices - Google Patents

Abstract

853,286. Cold-cathode tubes. STANDARD TELEPHONES & CABLES Ltd. May 17, 1957, No. 15792/57. Class 39(1). [Also in Groups XIX and XL(c)] Switching arrangements operating with pulse repetition speeds in excess of 300 Kc/sec. are obtained by connecting corona-primed diode glow discharge tubes, which are similar in form to known corona stabilizer tubes but are specially designed to have low formative delay and deionization times, in a modification of the circuit described in Specification 759,005 [Group XL(c)], or by connecting glow discharge tubes primed by an auxiliary glow or " artificial corona " discharge in the original circuit. The corona-primed diode glow discharge tube comprises a rod anode and a surrounding cylindrical cathode both of nickel, mounted in a standard sub-miniature glass envelope filled with a mixture of 20% hydrogen, 1% argon and 79% neon at a pressure of 250 mm. mercury. The internal diameter of the cathode is 1 mm., the cathode length 2 mm., and the anode diameter 0À076 mm. The tube is connected in a circuit (see Group XL(c)) in which the anode is connected through a high impedance to a 430 v. source to set up the corona priming discharge, and through a diode gate to a pulse source so that on coincidence of a pulse from this source and the receipt by the cathode of a pulse from the previous tube, the tube is fired, the corona discharge changing into a glow discharge. Fig. 7 shows a form of glow discharge tube primed by an auxiliary glow or so-called " artificial corona " discharge. A cylindrical cathode 9 surrounds an anode formed by a pair of axially separated tubular members 11 and 12 of which only the ends protrude into the cathode. A central wire 13 provides an auxiliary cathode and continuous glow discharges are maintained between the wire 13 and the anode members 11 and 12 during operation of the tube. In an alternative form, Fig. 8, the cathode is a hemispherical dome 31 drawn out in the base of a nickel cup 32. The anode 33 and auxiliary cathode 34 are provided by the respective tips of a pair of wires 35 and 36 sealed through a glass bead 37 which is fused to a ceramic disc 38 apertured to receive the wires and held in the cup 32 by a metal sleeve 39 which is bonded to the cup. Access to the interior of the electrode assembly is provided through an aperture 44 in the cup 32 in conjunction with a split spacing collar 45. The filling for each tube is the mixture described above but at a pressure of 200 mm. mercury, and the tubes are connected in the circuit described in Specification 759,005 with the addition of a connection from the auxiliary cathode 13 or 34 through a current limiting resistor to a negative voltage source of 150 v. Curves are given, Figs. 2 to 4 and 9 (not shown), plotting the variation of deionization time with anode-cathode voltage during an extinguishing pulse ; potential variation across a discharge gap for different electrode geometrics; variation of pre-breakdown and glow discharge currents with applied voltage ; and variation of formative delay time and deionization time with different electrode geometrics and gas fillings. Specifications 686,317 and 727,415 also are referred to.